[PD] Simple spectrum grapher in PD?
zmoelnig at iem.kug.ac.at
Wed Oct 29 12:48:28 CET 2003
Larry Troxler wrote:
> I searched the FFT examples directory in the doc, and can't find exactly what
> I'm looking for, which a patch that will periodically do an fft and write the
> spectrum to an array. This would be just for rough monitoring purposes - it
> would be fine if the FFT were only computed once per second for example, with
> a fairly small frame size, and the result written to an array for graphical
> viewing. I imagine that this is a reasonable and common request, but I can't
> find anything in the examples that does this.
well, simplest would be to not do the fft each second but rather each
blocksize. But then you will make quite a lot of fft's (depending on the
blocksize and overlap-factor). but i guess, on "modern" machines, this
might be only a small problem.
if you set the blocksize high (eg: 32768 samples) with no overlap at
all, you will get a significant peak in the CPU-load each time the fft
is calculated, and you might get clicks (depending on the audiobuf-size
and the cpu). of course you could use downsampling (see below), but the
downsampling stuff is really awful (i did it;-)), with almost no
filtering at all.
or you could turn on audio-processing with [switch~] whenever you want
to get the fft for a short time...
a more elegant solution would be the use of iemtab by thomas musil (but
i guess it is not released yet...?)
you can do fft's of tables (and other use- and harmful things to tables)
in message domain...
> Also, is there any documentation for "block~"? I seem to remember reading some
> somewhere, but now I can't find anything. "Help" on the right-click menu does
the reference is in doc/5.reference/switch~.pd
[switch~] and [block~] are really the same object, but [switch~] is
switchable while [block~] is not.
documentation for the up/downsampling feature of both of them can be
found at doc/3.audio.examples/J09.up.downsampling.pd (was
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